​​Is there a any adjective for describing people who like variety in their life?

( they cannot focus on one single job/ hobby/ relationship/ studying/ ...
They seek variety, they are neophiliac, and somehow adventuresome/ they have enthusiastic personality)

Can I say :

Variety seeking people/ variety seekers

A man/ woman of variety

See a translation

You can say
He/she is a neophiliac; I think it is the exact word you are looking for, but that is not a commonly used (or understood) term in colloquial language.

In commonly used language, we might say this just as you wrote it.
He/she can't focus on anything. He/she flits from one thing to another. (negative)
Or
He/she can't get serious about anything. He's/she's always on to the next new thing/adventure. (negative, but a little less so because of the 'adventure' aspect.)

On a positive side,
you could also say
He/she is multi-faceted.
which means the same thing but in a positive light. (Rather than 'can't focus, it carries the connotation of multi-talented, focusing on many interests.)

Hope this helps.